1. Field of the Invention
The invention concerns the manufacture of endless abrasive belts and cones and is particularly concerned with the splicing of the ends of a length of coated abrasive sheet material to form an endless belt or cone.
2. Description of the Related Art
For many years, endless abrasive belts and cones have been made by splicing the ends of lengths of coated abrasive sheet material. Two types of splices are common. In the so-called "lap" splice, the ends of the length are beveled by removing abrasive granules from one end and part of the backside from the other end, and the beveled ends are overlapped and joined adhesively as illustrated in U.S. Pat. No. 2,309,305 (Dahlstrom et al.). In the so-called "butt" splice, the backside at each end of a length of coated abrasive sheet material is scuffed to form a hollowed out space which is filled with an adhesive plus a strong, thin, tear-resistant splicing tape. Typically, each type of splice is formed in a heated splicing press to be of substantially the same thickness as the remainder of the belt or cone.
Most backings of endless abrasive belts and cones are cloth, paper, polymeric film, or laminates thereof. Cloth backings provide the most durable backings but are expensive and, to have suitably smooth surfaces, may require a series of coating treatments that can make cloth backings even more expensive. Paper and laminates of polymeric film and paper afford intermediate durability and are often used where cloth would be too expensive. For light duty, backings can be polymeric film, the backside of which usually has a resinous coating that is porous.
It is believed that most splices of current manufacture are made with an organic solvent solution of adhesive that penetrates into pores of the backing to enhance the strength of the splice. Heat is then applied to volatilize the organic solvent which pollutes the atmosphere unless expensive recovery apparatus is employed. Unfortunately, organic solvent vapors are inflammable so that their recovery is hazardous, but their release into the atmosphere is becoming environmentally unacceptable. The use of adhesive solutions for splicing endless abrasive belts is described in coassigned U.S. Pat. No. 3,154,897 (Howard) and in U.S. Pat. No. 3,763,604 (Malloy).
In U.S. Pat. No. 4,194,618 (Malloy), endless abrasive belts are spliced using a partially cured, heat-activatable preformed adhesive film which does not evolve any solvent. It is believed that such dry bonding films are little used in the manufacture of endless abrasive belts, perhaps due to a concern that a dry adhesive might not penetrate sufficiently into the backing to prevent the splices from failing prematurely when exposed to the heat, flexural fatigue, and other rigors to which belts and cones are subjected in ordinary usage.